Unfortunately I believe you are outside of the weight range for the stock Ti spring. Compensating for an incorrect spring rate with preload is not the way to go, as it will negate the benefit of running coil suspension in the first place by increasing the force required to get the fork moving from the zero travel point.

I weigh a less than you (180) and found the stock spring too soft, but you can try turning up the compression damping significantly and perhaps adding a bit of preload to get you by.